| 摘要 |
PROBLEM TO BE SOLVED: To obtain optical glass having a low partial variance ratio (&thetas;g, F) and suppressed in time dependent deterioration of spectral transmittance, while its refractive index (n) and Abbe number (&ngr;) lie within a desired range, and to obtain a preform and an optical element using the same.SOLUTION: The optical glass contains 10.0-40.0 mass% SiOcomponent and 1.0-50.0 mass% NbOcomponent based on the whole glass mass in a composition in terms of oxide, and has an Abbe number (&ngr;) of ≥15 to ≤30 and the partial variance ratio (&thetas;g, F) which satisfies the following relations for the Abbe number (&ngr;): (-0.00160×&ngr;+0.63460)≤(&thetas;g, F)≤(-0.00480×&ngr;+0.73500) in the range of &ngr;≤25, and (-0.00250×&ngr;+0.65710)≤(&thetas;g, F)≤(-0.00250×&ngr;+0.67750) in the range of &ngr;>25. |
